Sizing of Micro Cracks Using Laser-induced Broad-band Surface Waves.

Ochiai, Makoto; Butsuen, Takashi; Miura, Takahiro; Kuroda, Hidehiko; Soramoto, Seiki; Kanemoto, Shigeru

doi:10.3327/jaesj.43.275

Cited by 11 publications

(2 citation statements)

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“…(3) Optical mirrors and mechanical stages can scan the lasers, and information on ultrasonic propagation at multiple points can easily be obtained. With these features, it has been used for defect measurement [8,9] including the detection of internal defects [10][11][12][13]. In addition, there have been many research reports on plate thickness measurement [14] and material evaluation [15,16].…”

Section: Introductionmentioning

confidence: 99%

Study on Detecting Method of Internal Defects by Laser Ultrasonics in Lap Joint Welding of Galvanized Steel Sheet and Finite Element Analysis of Its Detectability

Okuyama,

Nomura,

Sano

et al. 2023

Applied Sciences

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Blowholes caused by vaporization of the galvanized layer are a problem with galvanized steel sheets, which use lap joint welding. The laser ultrasonic method is the possible solution to realize the desirable 100% inspection instead of the conventional sampling inspection. We have previously proposed a method to detect blowholes by capturing the reduction in ultrasonic intensity when it passes through internal defects through signal processing. However, there was a problem that the detection indicator devised varied. In this study, we investigated the causes and trends of detectability using finite element analysis. To efficiently calculate the results obtained by scanning measurement, we proposed and established a method to reproduce the results by taking the results from static measurements, which were shifted in the direction of the weld line little by little. As a result, it was found that one of the reasons for the detection indicator variation with scanning by the lasers is the three-dimensional positional relationship between the blowhole and the scanning measurement line. In addition, it was possible to propose the performance required for the ultrasonic generation laser such as the traveling speed and the repetition frequency by back-calculating the spatial resolution from the rate of detection needed.

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Section: Introductionmentioning

confidence: 99%

Study on Detecting Method of Internal Defects by Laser Ultrasonics in Lap Joint Welding of Galvanized Steel Sheet and Finite Element Analysis of Its Detectability

Okuyama,

Nomura,

Sano

et al. 2023

Applied Sciences

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“…One technique that enables laser-based TOFD is to use a laser-ultrasonics, which means an ultrasonic wave generation by a laser pulse and its detection by an optical interferometer [2]. Recently, a few techniques to size surfacebreaking cracks have been proposed by using laser-generated surface wave [3][4][5], although these can be useful only for the shallower cracks, say a depth of less than a few mm, in principle. TOFD technique combined with laser-ultrasonics has been also attempted by using surface-skimming wave [6] and bulk waves [7].…”

Section: Introductionmentioning

confidence: 99%

Laser Ultrasonic Study of Crack Tip Diffraction

Ochiai¹,

Lévesque²,

Talbot³

et al. 2003

AIP Conference Proceedings

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Ultrasonic diffraction pattern at a crack tip and crack depth sizing based on the diffraction are studied by using laser-generated bulk waves. Directivity patterns oriented essentially along the normal for the diffracted longitudinal wave and essentially at 45 (deg) for the diffracted shear wave for any incident angles is obtained. A laser-ultrasonic system combined with time-offlight (TOFD) analysis is produced and demonstrates accurate crack sizing on an artificial slot having a variable depth from 0 mm to 10 mm. An improvement of signal-to-noise ratio by split spectrum processing (SSP) is also suggested.

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